High-low pressure pump



Oct. 8, 1963 T. A. CAMPBELL ETAL HIGH-Low PRESSURE PUMP Filed 001.. 2.9,1959 4 Sheets-Sheet 41 f90/m45' ,4. CAM/@5ML dan? l. wv/1. Fez-p ,6.MEM/neo05' Oct. 8, 1963 T. A. CAMPBELL ETAL 3,106,320

HIGH-LOW PRESSURE PUMP 4 Sheets-Sheet 2 Filed Oct. 29, 1959 Oct 8, 1963T. A. CAMPBELL ETAL 3,106,320

HIGH-Low PRESSURE PUMP 4 sheets-sheet Filed Oct. 29, 1959 .lllllllll E,4 rra/e/vf/ Oct. 8, 1963 l T. A. CAMPBELL ETAL 3,106,320

HIGH-Low PRESSURE PUMP Filed Oct. 29, 1959 4 Sheets-Sheet 4 @PPP/M3,106,320 HIGH-LW PRESSURE PUMP K Thomas A. p Campbell, .lose L. Luna,and Fred R. Meinardus, Chicago, Ill., assiguors to Stewart-WarnerCorporation, Chicago, lil., a corporation of Virginia Filed Get. 29,1959, Ser. No. 849,476 9 Claims. (Cl. 222-318) This invention relates toportable, hand-operated pumps adapted for use with buckets, or likecontainers, of lubricant and more particularly to pumps of this typehaving both high and low output pressure.

While pumps of this type have been used in the past, such pumpstructures are relatively costly and complicated especially when thepumps are designedto provide both a high and a low liquid outputpressure. It is therefore an object of this invention to provide asimplified high and low pressure pump adapted to be used with acontainer of liquid such as lubricant or the like.

It is a further object of this invention to provide a high and lowpressure pump assembly wherein the container r bucket holding thelubricant or the like lluid may be replaced in a simplied operationrequiring much less time than that normally consumed by the priorstructures.

Other objects of `this invention will be pointed out in the followingdetailed description and claims `and illustrated in accompanyingdrawings which disclose, by Way of example, the principle of thisinvention and the best mode which has been contemplated of applying thatprinciple.

-In the drawings p FIG. 1 is a side elevation of view, partially insection of the supporting base, bucket,` cover, pump and clamp assembly;FIG. 2 isa top plan viewV of the apparatus shown in FIG. l; Y

FIG. 3 is a front elevational view, partially in section of the portionof the apparatus shown in FIGS. l and 2;

FIG. '4 is a front elevational view, partially in section of thelowermost portion of the high-low pressure pump forming a portion ofthis invention;

FIG. 4a is a front elevational View, partially in section of theremaining portion of the high-low pressure pump above that shown in FIG.4;

FIG. 5 is a front elevational view of the outer stationary cylinderforming a portion of the pump shown in FIG. 4;

FIG. 6 is a front elevational view of the intermediate cylinder forminga portion of the same pump;

' FIG. 7 is aibottorn sectional View of the cylinder shown in FIG.` 6taken along lines 7-7;

FIG. l8 'is a front elevational view of the inner cylinder of the pumpshown in FIG. 4;

FIG. 9 is a bottom sectional view of the cylinder shown in FIG. 8 takenalong lines 9 9; f

FIG. lpis a top plan view of the piston assembly of the pump shown inFIG. 4;

FIG. 11 is a plan view of the perforated retainer forming a part of thelower portion of the pump shown in FIG. 4.

In general,- the apparatus of this invention includes a supporting base,which is adapted to receive a generally cylindrical bucket holdinglubricant or. other uid to be pumped.v A Vsuitable 4circular cover isprovided which serves as a support for the longitudinally extendingreciprocating pump apparatus. In order to securely mount the containeror bucket in its supporting base as well i as to position the covercarrying the pumping apparatus upon `the top of the container, aplurality of circumferentially spaced latch assemblies are provided.These latch assemblies include a pivot rod whichrextends parallel toUnited States Patent O `ICC the sides of the container and a springbiased latch adapted to clamp the cover to the container and thecontainer to the base.

Another `feature of this invention resides in the simpliiied high andlow output pressure reciprocating pump which comprises in general; anouter stationary cylinder forming an enclosed Working chamber, a pistonrod adapted to move axially within the cylinder and spaced therefrom,and piston means mounted on the piston rod, in sealing relation with therod and cylinder. Means are provided for causing either the piston andthe rod to move together relative to the cylinder for effecting lowtluid output pressure or for causing only the rod to move relative tothe cylinder to yeect a high uid output pressure.

Referring to the'drawings, the bucket and pump assembly includes agenerally rectangular base member 2, upon which is positioned agenerally cylindrical reservoir 4 containing lubricant or other fluid tobe pumped. Mounted at the top of the reservoir 4 is a suitable cover 6of a generally circular shape and conforming to the diameter of thecylindrical reservoir 4. Suitably positioned on the cover 6 is thehigh-low pressure pump S, which for convenience is shown positioned atthe forward end of the cover in front of carrying handle 10i.

The high-low pressure pump is of the reciprocating piston and cylindertype including a pivotable lever l2 for causing the piston rod 14 toreciprocate within the main or outer stationary cylinder 16. Thearrangement for pivoting the operating lever 12, causing the piston rodV14, to reciprocate axially of cylinder i6, is conventional and thepresent invention is not directed to this feature. Referring to FIGS. 4and 4a it can be seen that outer, stationary cylinder i6 which defines apumping chamber at the lower end thereof, threadably `engages the cover6 at 13. Likewise, the lower end of the cylinder 16 threadably engages asuitable housing Ztl. The housing 2G includes a vertical bore 2d. Ailuid inlet valve 22 comprising a ball check valve is of the gravityoperated type wherein the ball 24 contacts seat 26 during downwardmovement of the piston assembly 28, while upward movement of the pistonassembly 28 allows the ball 24 to rise, the ball being prevented frommoving upward any great distance by the perforated disc-like retainer3l) which is positioned transversely of bore 21. A diagonal bore 32extends downwardly from bore 21 at generally right angles to the mainbore 21 of the housing 20. A second vertical bore 36 which is positionedgenerally parallel to the main bore 21 intersects the dii agonal bore 32and :is adapted to transmit the pressurized v having a diameter slightlygreater than the diameter of the diagonal bore 32, is spring biasedagainst seat 44 by means of biasing spring 42 to keep the outlet passageway or bore 36 sealed except when the ball check valve is unseated bythe pressurized lubricant as the piston assembly 28 moves downwardlyIwithin cylinder 16. A suitable ilexible hose 46 is connected to theoutlet bore 36 by means of a suitable screw threaded coupling 418. 'Ihehose 46 extends upwardly through the fluid body within the container andpasses through a suitable aperture 50 formed within the Icover 6. Inorder to seal the flexible hose I46 and the cover 6 a rubber gasket 52,FIG. 3, is positioned adjacent the outer surface ofthe cover andsurrounds the exible hose 46. A steel washer 54 is mounted on the top ofthe rubber gasket and suitable screws 56 provide suiiicient compressionforce to keep the rubber :gasket in place tightly compressed against theouter surface of the flexible hose 46.

Referring now to FIGS. 4 and 4a, the piston rod A14 Patented Oct. 8,1963k extends downwardly through a suitable opening 5S formed withincover 6 such that the rod may rotate and reciprocate freely within thecover and the main stationary cylinder 16. Suitable sealing means no areprovided to prevent egress of fluid between the relatively movablepiston rod 1d and the stationary cover 6. The piston rod 14 is of a twopart construction, the two parts of which are joined by means of a pin62. rl'his feature provides ease in assembiy and disassembly and may beeliminated if desired.

One feature of the present invention is directed to a simplified methodof providing both a high and low pressure output. The mechanism foraccomplishing this purpose is found generally within the outerstationary cylinder 16. The mechanism includes a piston assembly 2%which is adapted to move along with piston rod 14 within the outerstationary cylinder 16 during low pressure operation. During highpressure operation, the piston assembly remains stationary with respectto the cylinder 16 and the piston rod 14 itself reciprocates within boththe piston assembly 23 and the outer stationary cylinder 16. in order toaccomplish this, the piston assembly Z is provided with suitable sealingsurfaces which may be formed of a pair of somewhat exible disc members6d, the disc members being carried at the lower end of the pistonassembly by suitable spring clamping means 6d. The piston assembly 2Sfurther includes an integral, generally elongated, sleeve 65 whichextends upwardly within cylinder 16 for a distance which is roughly halfthe length of the cylindrical member 16. ln order to allow the pistonassembly 23 to move axially with respect to piston rod 14, but toprevent any rotatory movement between these two elements, the outerstationary cylinder 16 is provided with a suitable slot 78 shown in FIG.5, extending longitudinally of the upper portion of outer stationarycylinder id. rlhe upper terminal end 0f sleeve 63 is provided with apair of projections 72, shown in FGS. 4 and 10, which are of somewhatgreater diameter than the major portion of the sleeve 63 and of slightlyless diameter than the internal diameter of the outer cylinder 16. Oneof the projections 72 has a threaded central bore 74, adapted to receivea suitable screw 75 which extends outwardly through the elongated slot70 when the piston assembly 28 is positioned within the stationarycylinder 16. it is apparent therefore that the piston assembly 2S may bereciprocated within the cylinder 16 a distance determined by theelongated slot 76 while at the same time the piston rod 14 is freelyslidable and rotatable within the piston assembly 23 since there is nopositive connection between these elements. The sleeve 63 and the wholepiston assembly 28 moves with the piston rod 14 for low pressureoperation. However, the piston assembly 2S is stationary when the outputof the pump is adjusted for high pressure. 'Ehe ratio of high pressureto low pressure produced by the pump is determined by the relativecross-sectional areas of the piston assembly 28 as defined by theflexible disc member and the piston rod 14 since either the piston rod14 and the piston rod assembly 2% move together or the piston rod 14moves by itself.

The means for determining the stationary or moving condition of thepiston assembly 28 will now be described. An intermediate or second4cylinder or tube 78 is positioned concentrically in the outerstationary cylinder 16 at the upper end thereof. The intermediatecylinder is spaced slightly from the reciprocating piston rod `1f?, andextends upwardly within the enlarged bore St) past the threaded end 18of outer cylinder 16. The intermediate or second cylinder 78 includes alaterally extending slot 32 at the upper end thereof and the cover 6 isadapted to receive a threaded screw 84 such that the end of the threadedscrew 8d extends within the lateral slot 82. Yhis permits the second orintermediate cylinder 7S to be rotated on its axis but does not permitaxial movement thereof with respect to the outer stationary cylinder 16.

CJI

The prime -function of the intermediate cylinder is to prevent upwardmovement of the piston assembly during high pressure operation of thepump when only the piston rod reciprocates with respect to the outercylinder 16. The intermediate cylinder 78 is further provided with apair of longitudinal extended slots 86, FIGS. 6 and 7, which occupy thegreater length of the cylinder and extend completely to the bottomthereof. The piston rod 14, FlG. 4a, immediately above the pin 62, has alaterally extending bore 83 running completely through the centerhereof. A pair of actuator pins 9G and 92 are positioned within the boreSS in back-to-back relation and have elongated head portions jdextending from the piston rod 14. The head portions 94 of the actuatorpins are so positioned as to reciprocate within the elongated slots 86of inL rxnediate cylinder 73 when the pump is operating to deliver fiuidat low output pressure.

The pump assembly further includes a third or inner cylinder 96 which ispositioned within the intermediate cylinder 78 and includes, at theupper end, a pair of aligned apertures 93 which are also adapted toreceive head portions 94 of actuator pins 90 and 92. As best seen inFIG. 4a, the inner cylindrical member 96 is positioned such that themajor portion of the cylinder extends downwardly past the sleeve 63 ofpiston assembly 28. lt is apparent therefore, that when the actuatorpins and reciprocate within slots 36 of the intermediate cylinder 73,the inner cylinder 95 will move along with the pins. ln addition,whenever the pins 90 and 92 rotate as the piston rod ld is rotated, theywill cause the intermediate cylinder 73 to rotate therewith. Whether thepump is operating under high or low pressure conditions the innercylinder 96 will always reciprocate with the piston rod 14 due to thepin connection.

it is the rotation of the piston rod 14 that sets up the high and lowpressure conditions within the pump structure. ln order to insure thatthe piston assembly 28 will not move in response to reciprocation of thepiston rod 1li during the high pressure operation of the pump, the innercylinder 96 further includes a pair of diametrically opposed elongatedslots 160 which run almost the full length of the member' from a pointslightly below the transverse apertures 98 to the extreme lower end ofthe cylinder. The elongated slots 100 allow the member to receive theprojection 72 formed on the upper end of sleeve 63, FIG. l0. In likemanner, the intermediate cylinder 73 is also rotated by the actuatorpins 9) and 92 so that its elongated slot 86 will receive the sameprojections 72 to permit reciprocable motion of the sleeve 68 therein.Therefore, when operating under low pressure conditions, the innercylinder 96 carries the sleeve 68 with it when it is reciprocated by thepiston rod 14. ln order to provide a connection between reciprocatingpiston rod 14 and the piston assembly 28, the inner cylinder 96 isfurther provided with diametrically opposed slots 102, FlG. 8, which arepositioned at the upper end of the elongated slots tltl at right anglesthereto. In accordance with this arrangement, as the piston rod 14 ismoved downwardly, the actuator pins 90 and 92 will carry the inner orthird cylinder 96 along with piston rod 14. The projection 72 `will bereceived by the elongated slots 100 with the inner cylinder 96ltravelling down until the projection 72 contacts the upper end of theslots at surface 16M. When the apparatus has reached this position, thepiston rod 14 is rotated causing inner cylinder 96 to rotate in likemanner until the projections 72 move fully within slot 162. It isapparent therefore, that further reciprocation of the piston rod 14 ineither direction will cause a like reciprocation of the piston assembly23 through the connection of the projections 23 and slot 102. Since boththe piston assembly 28 and the piston rod 14 are moving in unison, lowpressure output is achieved.

To change from low pressure operation to high pressure operation of thepump, it is only necessary to disengage the projections 72 on sleeve 68from the diametrically opposed slots 162 so that piston rod 14`and innercylinder .96 may move relative to the piston assembly 28. Rotation ofpiston rod 14 allows the projections 72 to be aligned with the elongatedslots 100 to permit relative axial movement 'with respect to both theintermediate and inner cylinders. Referring to FIGS. 6 and 7, there isshownV at the lower end of the second cylinder 7 8 a pair ofdiametrically opposed slots 106 having an upper surface 103, 'the uppersurface 108. making contact with the projections 72 to prevent anyupward movement of the piston assembly 28 as the piston rod 14reciprocates.

While the various elements making up the reciprocating high and -lowpressure may be located in various positions relative to each other, themanner contemplated by the present invention allows piston rod 14 to'berotated in the order of approximately 60 degrees to change the operationfrom high output pressure to low output pressure. In order to aid theuser in operation of the pump, there is provided various indicia 110upon the cover 6 in order that the `position of the pump element inregard to high pressure and low pressure output operation may be readilyascertained. In order to change the position of the piston rod, there isincluded, a plug 112 which extends at right angles to the piston rodaxis and may be grasped by the user and rotated to the desired positionwith ease. The plug 112 is rigidly coupled tothe piston rod by suitablescrewed threaded coupling means 114, FIG. 3. Other appropriate means maybe utilized for rotating the piston rod to effect change from highpressure to low pressure operation. It is also apparent that the presentinvention makes use of the advantageous position ing of the carryinghandle such that when the lever 12 is in a down position, it is restingcompletely within the groove 116 formedA in the upper portion of handle10.

VChanging from high to low pressure or vice versa can be accomplishedonly at the downward end of the stroke so that inadvertent changes'willnot occur during pumping.

The present invention is also directed to providing a compact, readilyassembled unit including a base member, a suitable container, a coversupporting the high and low pressure pump and the means for holding theelements in assembled relation while allowing easy and quick removal andreplacement of the container carrying lubricant or other liquid to bepumped. Referring to FIGS. 1 and 2, the assembly includes a generallyrectangular base member 2 which may be formed of U-shaped metal stockhaving a width slightly less than the diameter of the tank or containerholding the lubricant and having a length somewhat greater than thisdiameter. The container or bucket 4 is formed of sheet metal. Containersof this type are generally uniform in nature. However,

with the type of latching means employed by the present invention,slight variation in the height of the container or bucket may readily betaken care of inherently by the support means. The cover 6 is alsoformed of metal, and may be of cast or forged construction. Pertinent tothe present invention is the placement of a number of circompressionspring 136 which tends to force the barrel downwardly on the rod 124.The latch member 122 is rigidly coupled to the barrel 134 and includes alatch extension member 140 which cooperates with a U-shaped p grooveformed within member 120, to effect a latching operation. It is readilyapparent that the biasing spring 136 acts to frictionally seat the cover6 on the container 4 while at the same-time securely holding the coverand container upon the base 2. When setting up the pump or changing thecontainer 4, it is only necessary to movev the latch 122 upwardlyagainst the bias or" spring 136 and pivot the rods 124 with respect tothe base and away from the container. In order to accomplish this, thelatch members 122 include a ring 141 formed integrally at the upper endthereof such that the user may place one linger within the ring and pullupwardly against the spring tension. This simplified construction forholding the assembled parts in position during use of the pump makespossible the expenditure of minimum time and eiort for replacing thelubricant containing buckets when they are empty. In addition, somevariation in bucket size and height may be permitted without requiringdifferent support means.

While the fundamental novelty features of the invention as applied -tothe preferred embodiment have been shown and described, it will beunderstood that various omissions and substitutions and changes in theform and details of the device illustrated and in its operation may bemade by those skilled in the art without departing from the spirit ofthe invention. It is the intention, therefore, to be limited only asindicated by the scope of the following claims.

What is claimed is:

1. A high and low output pressure pump for substantially incompressiblefluid disposed within a vessel, comprising a tirst stationary cylindersecured Within the vessel and adapted to have at least the lower portionthereof submerged in the liuid, a piston rod adapted to reciprocate androtate within said first cylinder spaced therefrom and Y projectingYoutside ofv the vessel through a top opening therein, piston meansslidably mounted on the lower end portion of said piston rod in sealingrelation thereto and to the lower portion of said first cylinder, andforming within said lower portion of the iirst cylinder a pumpingchamber, inlet and outlet check means for the first cylinder adapted tocheck iiuid Within the vessel to and from the pumping chamber, a secondcylinder positioned within the remaining upper portion of said firstcylinder and surrounding said reciprocating piston rod adjacent saidpiston means, said remaining portion of the first cylinder and thepiston means remote of the pumping chamber communicating with said iiuidwithin the vessel, connecting means formed on said second cylinderwithin said remaining portion of the first cylinder and adapted tocouple said piston rod to said piston means when the piston rod isrotated to a irst position and to allow relative movement between saidpiston rod and said piston means when cumferentially spaced upstandingflanges 120 along the outer periphery of the cover. The flanges have agenerally U-shaped configuration along the upper surface so as toreceive appropriate latch members 122. A number of verticallypositionedrods 124 are mounted on the base member 2 which are providedwith suitable apertures 126 for receiving the lower terminal ends of therods. Since a portion of the rod 124 is turned back on itself as at 128after the rod has been positioned within the hole 126, the rods willremain semi-lixed to the base 2 but will pivot somewhat at the pointwhere the rod passes through the aperture 126. The upper end of each ofthe rods 124 includes a circumferential groove 130 which is adapted toreceive a C-shaped retaining ring 132. Mounted for reciprocation uponthis end of the rod is a barrel element 134 which is prevented frommoving oli. the end of the rod by the-retaining ring 132. Positionedbetween the retaining ring 132 and the bottom of the barrel V134 is athe piston rod is rotated to a second position.

2. An improved high and low output pressure fluid pump for substantiallyincompressible fluid disposed within a vessel, comprising a firststationary cylinder, a piston rod adapted for rotation and reciprocationwithin said cylinder, piston means slidably mounted on said rod insealing relation with said rod and said cylinder to define within aportion thereof a working iiuid chamber,` inlet and outlet cheek meansfor the fluid chamber, means in the iirst Y cylinder remote of theworking chamber having direct connection to the iiuid in the vessel, asecond cylinder positioned within said tirst cylinder between said rodand said tirst cylinder adjacent said piston means, means allowinglimited rotation of said second cylinder about its axis while preventingaXial .movement thereof, a third cylinder positioned within `said secondcylinder coaxially ofk said rod, adjacent said piston means, meansconnecting said piston rod and said third cylinder whereby said thirdcylinder moves with said piston rod, Said third cylinder including atleast one longitudinal slot formed therein, said third cylinder furtherincluding a laterally extending slot formed therein adjacent saidlongitudinal slot at the end remote from said piston means, a stop meansassociated with said piston means, said stop means adapted to moveupwardly within said longitudinal slot and laterally within said lateralslot to lock said piston means to said third cylinder during lov.pressure operation, while during high pressure output, said stop meansreciprocates within said longitudinal slot whereby only said piston rodmoves relative to said first stationary cylinder.

3. An improved high and low output pressure fluid pump for substantiallyincompressible fluid disposed within a vessel, comprising a firststationary cylinder adapted to be positioned within the vessel, a pistonrod positioned within said cylinder adapted to rotate and reciprocatewith respect thereto and projecting from the vessel, piston meansslidably mounted on said piston rod in sealing -relation with said rodand a portion of said cylinder to define therewith a fluid chamber,fluid inlet and outlet check means for the liuid chamber, the portion ofsaid cylinder remote from said fluid chamber having direct communicationwith the fiuid in said vessel, a second cylinder positioned within saidfirst cylinder between said rod and said first cylinder adjacent saidpiston means, means rigidly connecting said second cylinder and saidpiston rod, said second cylinder including at least one longitudinalslot extending a portion of the length thereof, at least one lateralslot formed within said second cylinder and intersecting saidlongitudinal slot, stop means formed on said piston means, said stopmeans adapted to be received by said longitudinal and said lateralslots, whereby actuation upon the projected end of the piston rodincluding axial movement and rotation thereof to a rst position effectscoupling of said piston rod to said piston means to effect low pressureoutput, while rotation of said piston rod to a second position causessaid stop means to reciprocate longitudinally within said longitudinalslot to effect high pressure output of said pump.

4. Apparatus as claimed in claim 3 further including means forpreventing rotation of said piston means during recipi'ocation thereof.

5. Apparatus as claimed in claim 4 wherein said means recited in claim 6comprise: a longitudinal slot formed within said first cylinder, andprojecting means mounted on said piston means, said projection meansadapted to extend outwardly within said longitudinal slot for guidingsaid piston means along a longitudinal path while preventing rotation ofsaid piston means with respect to said stationary cylinder.

6. Apparatus as claimed in claim 3 further including means forpreventing upward movement of said piston means under high pressureoutput conditions.

7. Apparatus as claimed in claim 6 wherein said means comprise: anintermediate cylinder positioned within said first stationary cylindercoaxially of said piston rod between said second cylinder and said outerstationary cylinder, means for mounting said intermediate cylinder forlimited rotary movement but preventing axial movement thereof, stopmeans formed on said intermediate cylinder, said stop means adapted tocontact said stop means formed on said piston means for preventingupward movement of said piston means when said piston rod is rotated tosaid second position.

8. An improved high and low output pressure fluid pump forsubstantiallyincompressible fluid disposed within a vessel, comprising afirst stationary cylinder adapted to be positioned within the vessel, apiston rod positioned within said first cylinder for rotation andreciprocation therein and projecting from the vessel from a top openingtherein, piston means slidably mounted on said piston rod in sealingrelation with said rod and at least a portion of said cylinder andforming therewith a fluid chamber, fluid inlet and outlet check meansfor the fluid chamber, the remaining portion ef the first cylinderremote from the fluid chamber having means therein providing directconnection to the fluid in the vessel, means for preventing rotation ofsaid piston means but allowing rcciprocation thereof with respect tosaid first cylinder, coupling means formed on said piston means, anintermediate cylinder positioned within said first cylinder coaxial ofsaid piston rod, means for mounting said intermediate cylinder withinsaid first cylinder for limited rotation with respect to said firstcylinder but preventing axial movement therewith, said intermediatecylinder including at least one elongated slot extending the majority ofthe length of said intermediate cylinder and adapted to receive saidcoupling means, an inner cylinder positioned within said intermediatecylinder coaxially of said rod and coupled thereto, adjacent said pistonmeans, said inner cylinder including at least one second elongatedlongitudinal slot extending along a portion of said inner cylinder awayfrom the end of said inner cylinder adjacent said piston means, saidinner cylinder further including at least one laterally extending slotat the end of said second longitudinal slot remote from said pistonmeans and intersecting said second longitudinal slot, said lateral andlongitudinal slots adapted to receive said coupling means, wherebyactuation including rotation and reciprocation of said piston rod uponthe projected end thereof to a first position causes said coupling meansto slide within said longitudinal slots of said intermediate and innercylinders and to rotate in said laterally extending slot to lock saidpiston rod and said piston means together to effect low output pressureoperation of said iiuid pump while rotation of said piston rod to asecond position allows said coupling means to move freely, relative tosaid longitudinal slots of said intermediate and said inner cylinderswhereby only said piston rod moves relative to said first stationarycylinder to effect high output pressure of said fluid pump.

9. Apparatus as claimed in claim 8 wherein said intermediate cylinderincludes at least one longitudinally extending slot formed at an angleto said first longitudinally extending slot, said second longitudinallyextending slot being of a length much shorter than the firstlongitudinally extending slot, whereby rotation of said piston rod tosaid second position allows limited axial movement of said couplingmeans within said second slot formed within said second cylinder butprevents further upward movement of said freely siidable piston meanswithin said first stationary cylinder.

References Cited in the file of this patent UNITED STATES PATENTS

1. A HIGH AND LOW OUTPUT PRESSURE PUMP FOR SUBSTANTIALLY INCOMPRESSIBLEFLUID DISPOSED WITHIN A VESSEL, COMPRISING A FIRST STATIONARY CYLINDERSECURED WITHIN THE VESSEL AND ADAPTED TO HAVE AT LEAST THE LOWER PORTIONTHEREOF SUBMERGED IN THE FLUID, A PISTON ROD ADAPTED TO RECIPROCATE ANDROTATE WITHIN SAID FIRST CYLINDER SPACED THEREFROM AND PROJECTINGOUTSIDE OF THE VESSEL THROUGH A TOP OPENING THEREIN, PISTON MEANSSLIDABLY MOUNTED ON THE LOWER END PORTION OF SAID PISTON ROD IN SEALINGRELATION THERETO AND TO THE LOWER PORTION OF SAID FIRST CYLINDER, ANDFORMING WITHIN SAID LOWER PORTION OF THE FIRST CYLINDER A PUMPINGCHAMBER, INLET AND OUTLET CHECK MEANS FOR THE FIRST CYLINDER ADAPTED TOCHECK FLUID WITHIN THE VESSEL TO AND FROM THE PUMPING CHAMBER, A SECONDCYLINDER POSITIONED WITHIN THE REMAINING UPPER PORTION OF SAID FIRSTCYLINDER AND SURROUNDING SAID RECIPROCATING PISTON ROD ADJACENT SAIDPISTON MEANS, SAID REMAINING PORTION OF THE FIRST CYLINDER AND THEPISTON MEANS REMOTE OF THE PUMPING CHAMBER